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Proceedings Paper

GPR H-plane antenna patterns for a horizontal dipole on a half-space interface
Author(s): Stanley J. Radzevicius; Jeffrey J. Daniels; Chi-Chih Chen
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Paper Abstract

GPR dipole antenna patterns can be described by the interference of space and lateral waves. Because this is an interference phenomenon, antenna patterns are a function of frequency, distance, and electrical properties. Traditional far-field criteria based on dipoles in a whole-space are insufficient to describe dipole antennas on a half-space boundary. Whole-space criteria fail because they do not take into account the interference of space and lateral waves. The travel time difference between space and lateral waves increases as the angle of observation from vertical increases, or with increasing distance from the source. The result is increased interference and more abundant lobes with increasing distance and observation angle. Since GPR investigations are limited by attenuation and many environmental and engineering targets of interest are located within a few wavelengths of the antenna, asymptotic solutions do not accurately describe antenna patterns for most GPR applications. The exclusion of lateral waves in geometric optics solutions is another source of error for many GPR applications. Data were measured over a water filled tank to verify FDTD antenna pattern models. Asymptotic solutions predict H-plane peaks at an angular distance equal to the critical angle. Measured and modeled antenna patterns are broader and have peaks located at a larger angular distance, than predicted from asymptotic solutions. The peaks approach and decrease the rate of convergence toward the asymptotic solution with increasing distance from the source, and data modeled over water demonstrate that the peaks still do not converge to the asymptotic solution at a distance of 24 wavelengths. The low directivity of dipole antennas explains why out of the plane reflections are commonly observed in GPR data.

Paper Details

Date Published: 27 April 2000
PDF: 6 pages
Proc. SPIE 4084, Eighth International Conference on Ground Penetrating Radar, (27 April 2000); doi: 10.1117/12.383504
Show Author Affiliations
Stanley J. Radzevicius, The Ohio State Univ. (United States)
Jeffrey J. Daniels, The Ohio State Univ. (United States)
Chi-Chih Chen, The Ohio State Univ. (United States)

Published in SPIE Proceedings Vol. 4084:
Eighth International Conference on Ground Penetrating Radar
David A. Noon; Glen F. Stickley; Dennis Longstaff, Editor(s)

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